Shale gas reservoirs with low porosity and low permeability are considered to be complex types in the world of oil and gas fields. One of the main challenges associated with these reservoirs is the relationship between pressure and water resources, as initiating gas flow requires exceeding a certain threshold known as the “threshold pressure gradient” (TPG). This article addresses a comprehensive study in the Ordos Basin on the influence of water content in tight shale gas reservoirs on the threshold pressure gradient under varying conditions of water saturation and formation pressure. By conducting experiments and developing a mathematical model, we explore the factors affecting TPG, contributing to enhanced gas production strategies and effective reservoir management. This article will reveal how this research helps tackle the challenges facing the gas industry due to geological and hydrological complexities.
Characteristics of Tight Gas Sand Reservoirs
Tight gas sand reservoirs are of great interest in the field of oil and gas exploration due to their vast reserves and development potential. These reservoirs are characterized by unique properties, such as low porosity and low permeability compared to conventional reservoirs. These features complicate the fluid flow process within the reservoir, as they contain a complex arrangement of pores that facilitate intricate interactions between water and gas. Studies on tight gas sand reservoirs, such as those found in the Ordos Basin in China, provide insights into the geological and physical complexities prevalent in these areas.
Tight gas sand reservoirs contain fine and complex pores, which lead to the difficulty of gas flow. The reduction in permeability is a key point that enhances the challenges associated with natural gas production. Gas present in these reservoirs requires specific pressure conditions to initiate flow, known as the threshold pressure gradient (TPG), which is the critical point that must be surpassed to begin gas flow. Studies indicate that TPG is influenced by factors related to water saturation and formation pressure, confirming that exceeding 50% water saturation leads to significant changes in TPG.
Through laboratory experiments, the existence of TPG in tight gas reservoirs has been verified, and an inverse relationship between TPG and reservoir permeability was found. As the permeability of the reservoirs decreases, this results in an increase in the TPG value required to initiate gas flow. Therefore, these measurements and standards are essential for enhancing the management of tight gas sand reservoirs and developing production strategies.
Impact of Water Saturation on TPG
Water saturation is considered a vital factor influencing TPG, as increasing water saturation leads to a significant reduction in TPG. Research indicates that higher water content in reservoirs contributes to reducing the ability of gas to flow, due to the water films that form at the narrow pores, which impede gas movement. These films create additional resistance that gas must overcome before it can move.
When water saturation exceeds 50%, a larger change occurs in TPG, indicating that traditional reservoir management strategies require review and thorough examination under varying water saturation conditions. Understanding how water saturation levels affect TPG aids in determining production enhancement measures, such as employing techniques like hydraulic fracturing to increase permeability and reduce TPG.
Additionally, results indicate that reservoirs with weak permeability exhibit greater changes in TPG with pressure variations compared to reservoirs with high permeability. This highlights the importance of managing the surrounding conditions of the reservoir, such as pressure and saturation, to achieve appropriate adjustments in production strategies.
Pressure and Its Effects on TPG
Studies indicate that formation pressure plays a significant role in its effect on TPG. As pressure increases, its effects on TPG stability improve. Within a high-pressure range, it is observed that the stability of the gas becomes more pronounced, especially when local pressure exceeds 25.0 megapascals. This leads to a reduction in the slip effect of gas molecules, thus achieving stable TPG.
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high pressure in simplifying gas flow by changing the interaction of gas with water in rocks. Pressure control is a crucial factor in improving the gas extraction process from tight gas reservoirs. The balance between pressure and water saturation can contribute to better production management.
A mathematical model has also been developed to predict TPG based on characteristics such as permeability, water saturation, and formation pressure. This model requires a deep understanding of the physical properties and interactions in the area. These models are an important tool for production and improving existing strategies.
Practical Applications and Future Research
These discoveries contribute to enhancing the management of tight sandstone gas reservoirs. Finding technological solutions that can address the challenges associated with gas flow under specific pressure and acceleration conditions is required. Through a combination of laboratory experiments and theoretical approaches, new strategies can be developed that incorporate the reservoir body and the techniques applied.
Maintaining sustainable reservoir performance is a key aspect, as managing water content enhances production efficiency. Modern technologies are employed to ensure that permeability enhancement methods are utilized.”””
This indicates that future research should focus on studying various environmental parameters and their impact on TPG and developing more accurate models. Research should strengthen the relationship between ground conditions and the techniques used in the gas development process.
Improving production capacity to overcome complex challenges requires considering various aspects, including pressure effects, the need to enhance permeability, and a better understanding of water behavior in reservoirs. Ultimately, the great importance of understanding TPG manifests in improving gas production and related services, enabling companies to make better decisions in development strategies.
The Effect of Fluid Components on Hydrostatic Pressure in Rocks
This section addresses the impact of changes in fluid components on hydrostatic pressure in rocks, citing previous studies that highlighted the importance of understanding this effect on gas flow. Zeng et al. (2010) studied the effect of different fluids on measured hydrostatic pressure (TPG) and presented a mathematical model that relies solely on fluid properties, ignoring rock properties. On the other hand, Liu (2023) noted that as production time increases, the gas flow area expands, and flow resistance decreases, indicating the importance of rock resistance in determining TPG. This necessitated the development of a mathematical model that considers the influence of the interaction between fluids and rocks.
Studies, such as those by Yang et al. (2015), incorporated equations that consider rock permeability and water saturation degree, but the developed models often operated under normal pressure conditions, meaning that the impact of formation pressure was overlooked. In this context, a dynamic testing device was proposed to measure TPG pressure in tight gas rocks under various water saturation conditions, reflecting the actual production reality. These studies reveal an urgent need for further research to better understand the impact of these factors on gas flow capacity, especially in sources with low permeability.
Material Settings and Testing Procedures in Experiments
This section focuses on the preparation of the materials used and the procedures followed in the experiments. Rock cores were taken from four different samples of tight gas reservoirs in the Ordos Basin, and the properties of these cores were measured using methods based on Boyle’s Law and the pulse decay method. This process requires measuring porosity and permeability to accurately determine reservoir conditions, which are a reliable basis for any subsequent experiments.
The procedures included first cleaning the samples, then drying them for a specified period, before placing the cores in intermediate containers under low pressure to ensure the saturation of the outcrop with water. Then, ambient pressure is applied using ambient pressure pumps, allowing gas flow experiments to be conducted under stable conditions. Maintaining constant pressure and keeping water saturation below 2% are essential conditions for accuracy that must be achieved for measurement purposes, as this ensures that gas flow is not affected by unnecessary liquid phases.
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Through the different volatile estimation methods, the team was able to evaluate TPG with greater accuracy. Flow experiments were conducted until complete flow curves were obtained, which reflect the dynamic effects of fluid properties and allow for predictions on how gas reservoirs behave under various conditions. These processes represent a critical step towards understanding the complex dynamics that govern tight gas reservoirs and assisting them in achieving more accurate production outcomes.
Results of Water Saturation Effect on TPG
Initial experiments showed clear effects of water saturation on the hydrostatic pressure in the tested samples. In particular, TPG is significantly affected by the saturation rate; results demonstrated that TPG increases significantly with increasing water saturation. When analyzing samples from different layers, a consistent pattern emerged where gas reservoirs with low permeability exhibited higher TPG compared to their high permeability counterparts.
At the same saturation level, results showed that the gas flow was gradually declining, indicating that the apparatus in which the experiment is conducted is highly influenced by the actual conditions of the rocks and how they interact with water. The data presented from the experiments exhibited clear curves reflecting the increase in hydraulic activity with density, which results from the Jaman effect, where an interaction occurs between gas and liquids, leading to increased resistance and negative effects on gas conductivity.
Through the analysis of different cap rock layers, sharp changes in TPG were recorded indicating that at saturations above 50%, there is a clear shift in TPG behavior. This means that gas reservoirs have significant amounts of trapped gases that require higher pressure to overcome the liquid resistance, necessitating the improvement of production strategies for better results. Compiling data from different samples provided researchers with a powerful tool to understand the complex behavior of tight gas reservoirs and how to optimally plan for their exploitation.
The Relationship Between Formation Pressure and TPG
The research aims to clarify the relationship between formation pressure and TPG, where different pore pressures were assigned from 15 to 30 MPa and the involved peripheral dimensions to ensure stable permeability conditions. The experiments were conducted based on various pressure conditions to allow identification of the required pathways to understand how they affect the performance of gas reservoirs. The results enhanced the ability to envision how pressure changes could affect the mobility efficiency in rocks, including gas-liquid contact pathways.
As formation pressure increases, a significant rise in the normalized TPG ratio was observed, highlighting the impact of pressure on the propulsion strength in gas reservoirs. However, this is related to other factors such as swelling ratio, which directly affects TPG through imbibed fluid effects. These dimensions can be better explained through in-depth analysis of the experiments, reflecting the interrelated relationships between kinetic properties, pressure, and various factors involved in the production process.
By compiling data from the experiments, researchers were able to determine that the increase in pressure translates to an increase in the force required to pass gas through narrow spaces. Consequently, it became their obligation to develop models to mathematically interpret this relationship, thereby increasing the accuracy of predictions based on these relationships, which is considered a significant factor affecting production strategies in the sector.
The Effect of Formation Pressure on Gas Flow in Tight Gas Rocks
The gas flow properties in tight gas rocks are significantly influenced by formation pressure. Studies have shown that as formation pressure increases, the average gas pressure gradient (TPG) decreases in low-permeability rocks. Under low pressure conditions, the gas flow rate is higher due to the Slippage Effect, where gas particles move more freely in narrow pores compared to liquids, enhancing gas permeability. When local pressure exceeds 25 megapascals, the Slippage Effect begins to dissipate, leading to a general stabilization of the pressure gradient. In tight gas rocks, the distances between particles are greater at low pressures, which allows for more free movement, thus resulting in higher gas permeability.
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For example, in rocks that have a permeability of less than 0.1 milliDarcy, it was observed that the pressure gradient decreases significantly in relation to the increase in pressure, with a decrease of 19.68%, 44.93%, and 39.68% as the pressure increased to 15 and 30 megapascals, respectively. In contrast, for rocks with permeability above 1.0 milliDarcy, the changes were less pronounced, indicating clearer stability in flow with increasing pressure.
Mathematical Model for Determining Dynamic Pressure Gradient
The effect of water saturation on the dynamic pressure gradient (TPG) was studied by setting up a mathematical model that links TPG with water saturation and formation pressure. The resulting mathematical equation, which expresses this relationship, is of great importance in predicting gas behavior in different rocks. The equation depends on multiple parameters such as pressure and oil saturation, allowing for better dynamic analysis of gas movements within the rocks.
One of the mathematical models developed shows variation in values based on a set of data collected. The equations obtained link TPG to permeability and saturation and demonstrate significant convergence between theoretical and practical values when applied to specific rocks, indicating the critical importance of these models in assessing and predicting gas behavior in reservoirs.
Using these equations, a graph can be prepared to illustrate the relationship between TPG, pressure, and saturation levels, contributing to a better understanding of how to manage gas reservoirs effectively. The study indicated that saturation has a greater effect on TPG compared to pressure, emphasizing the importance of periodically monitoring the water content in tight gas rocks to ensure production efficiency.
Analysis of Results and Practical Applications in Developing Tight Gas Reservoirs
The obtained results are based on detailed studies in the Ordos Basin in China, where necessary experiments and analyses were conducted to understand how pressure and water saturation influence hydrodynamic properties. Based on the collected data, it was confirmed that it is essential to consider changes in water content during the development phases of tight gas reservoirs, as these changes significantly contribute to improving production strategies.
Applying the results can lead to better oversight of gas reservoirs, especially in areas facing permeability challenges. The move toward improving management strategies requires careful study of factors such as permeability, saturation, and pressure, which means that the production strategy should adapt to the specific geological characteristics of each reservoir.
When considering the development of gas reservoirs, studies should always be coupled with practical data. Utilizing experimental data can provide valuable insights into how gas interacts with rocks under various conditions. This knowledge is not only important for academic purposes but plays a central role in improving production and ensuring the sustainability of natural resources.
Research Results and Future Perspectives in Geological Studies
A profound understanding of the factors influencing gas flow in tight gas reservoirs is a pivotal step in geology and petroleum engineering. The results achieved demonstrate the complex links between pressure, saturation, and the physical properties of rocks, paving the way for the development of more efficient future production strategies.
With the advancement of technologies and mathematical methods, the developed models can be used to provide more accurate estimates of gas behavior, supporting innovations in production strategies. It is essential to integrate data from actual production to bridge the gaps between theory and practical application, contributing to enhanced performance and achieving environmental and economic goals.
Given the importance of studying the effects of pressure and saturation, scientists and engineers must engage in further research to expand understanding of the complex geological changes, including infrastructure and risk analysis. The future presents diverse opportunities to uncover new details in the gas world of oil and gas companies, necessitating collaborative efforts to improve sustainability and reduce economic risks.
Study
Properties of Tight and Water Sands
Tight and water sands represent one of the important topics in the field of earth sciences and the exploration of natural resources. According to recent studies, these sands have unique properties that affect how fluids flow and the associated risks of extracting gas and oil from them. Research has examined the correlation between pressure and hydrological properties, including impacts on productivity.
For example, it should be noted that tight sands often suffer from low fluid permeability due to small pores. This negatively impacts the production capacity of oil and gas fields. In specific cases, mathematical models have been applied to simulate the flow behavior in these sands where it has been claimed that the minimum pressure required can significantly influence the long-term production of the field.
These studies are particularly essential in the Ordos Basin where the sites are rich in resources. Understanding these processes helps improve extraction techniques and increase production efficiency.
The Importance of Boundary Pressure and Its Impact on Flow
A deep examination of the impact of boundary pressure, especially in tight sands, has shown a critical role in the flow of water and gas through certain environments. Research indicates that boundary pressure refers to the minimum threshold required to initiate fluid flow through the pores. Weakness in this property can lead to production loss or reduced performance.
For example, in the case of low productivity sands, experimental tests on boundary pressure were conducted, and results showed that the presence of compressed water within the pores complicates the flow of oil, requiring special processing techniques for reprocessing and maximizing energy release.
The dynamic analysis of boundary pressure is also important for understanding production from wells. Advanced equipment can be used to measure pressure and identify the factors that affect it, such as porosity and geological characteristics.
Production Maintenance Techniques in Challenging Environments
As a result of the challenges posed by tight sands, strategies and procedures have been developed to improve production performance. Advanced techniques such as hydraulic fracturing and fluid injection are employed to enhance gas and oil flow. These methods rely on using hydraulic energy to create fractures in the rocks, thus facilitating fluid flow.
However, these techniques are not without consequences. Hydraulic fracturing can make the local environment susceptible to pollution risks and may alter the characteristics of the rocks, thereby affecting long-term production. Therefore, sustainability and environmental preservation are among the priorities of research and development in this field.
Moreover, companies are investing in research for safer and more effective alternatives aimed at reducing emissions and environmental impacts. These solutions may include using renewable energy technology in operations and maintaining the local environment.
Future Challenges and Research Trends
As technologies advance in the exploration and production of resources, challenges remain. The industry needs to address issues like sustainability, reducing environmental risks, and extraction costs. There is a continuous need for investments in research and development to gain a deeper understanding of the properties of tight sands, including improving their energy storage capabilities.
Future research is expected to lead to new discoveries that enhance the understanding of intricate interactions in those environments, with the potential adoption of new technologies such as computational modeling and remote sensing. For instance, these discoveries can provide new standards for water treatment and safe gas leakage.
The growing trends toward clean and renewable energy may also contribute to improving traditional extraction solutions, identifying ways to enhance production with less environmental impact. Future researchers are expected to play a significant role in proposing new methods to address the challenges associated with production from tight and water sands.
Gas Development in Tight Sand Reservoirs
Gas reservoirs are considered significant unconventional energy sources, containing vast reserves of gas with immense development potential. The share of these reservoirs is increasing in oil and gas exploration and development, making them a fundamental source in the energy sector. Projections indicate that annual production from tight gas reservoirs in China could reach around 600 × 10 cubic meters by 2030. For example, the Ordos Basin in China contains substantial gas reserves and hosts some of the most advanced gas fields. Gas reservoirs in this basin are characterized by low permeability and porosity, posing significant challenges for gas development.
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the challenges associated with these reservoirs a large amount of water, which negatively affects the production capacity of gas wells. The natural low productivity and the complexities of the remaining gas distribution leakage mechanisms pose a barrier. Therefore, these factors contribute to the reservoir deterioration and reduce the efficiency of gas field development, making it difficult to achieve stable long-term production in low-permeability, water-rich gas reservoirs.
Factors Affecting Flow and Pressure in Gas Reservoirs
Closed gas reservoirs are characterized by complex geological properties, including poor reservoir characteristics, strong variations in composition, low porosity, low permeability, and high water saturation. Under water-rich conditions, complex interactions occur between water and gas within the reservoir, complicating fluid flow mechanisms. Studies have shown that in gas reservoirs with low permeability, the flow paths of gas and water are very narrow, facilitating the formation of water films at the pore entrances.
The minimum pressure gradient required to overcome the resistance of these films is known as the threshold pressure gradient (TPG). Under ideal conditions, gas flow follows Darcy’s law, where the flow rate and pressure gradient exhibit a linear relationship. However, in low-permeability media, gas flow deviates from Darcy’s law, leading to a partially nonlinear relationship between flow rate and pressure gradient. Several factors influence TPG, such as reservoir permeability, water saturation, and pressure within the formation, making it crucial to understand these factors for developing production strategies.
Production and Pressure Enhancement Techniques
Research shows that the productivity of gas wells decreases as TPG increases. Higher TPG requires greater pressure differentials to initiate fluid flow, directly leading to reduced production. Therefore, it is essential to take measures to lower TPG, such as enhancing reservoir permeability through techniques like hydraulic fracturing. This requires careful management of production pressure differentials to prevent a decline in gas production efficiency due to excessive pressure variations.
The laboratory methods used to determine TPG include two main approaches: steady-state and unsteady-state. The steady-state method is particularly effective for directly measuring TPG, as it involves monitoring the minimum pressure required to maintain a steady flow rate through the sample. In contrast, unsteady-state methods are faster to implement and provide insights into the dynamic flow behavior and transient effects associated with TPG. Although unsteady-state methods may not provide a direct measurement of TPG like the steady-state method, they offer insights into the dynamic phenomena related to flow.
Mathematical Models and Their Applications for Production Performance
Many researchers have conducted studies on mathematical models describing the initial pressure gradient across different types of reservoirs. Experimental data showed a clear inverse relationship between TPG and reservoir permeability: as permeability decreases, the required TPG value increases. This indicates the importance of understanding the relationships between these parameters when developing production strategies. For instance, Zhu et al. noted that TPG increases in low-permeability reservoirs as water saturation levels rise.
Developing mathematical models addressing the relationship between TPG, reservoir permeability, water saturation, and pore pressure is essential to enhance gas production efficiency. These models provide the foundation for understanding the interactions between these variables and guiding strategic decision-making in production operations. The inputs and applied laws in mathematical models are crucial for achieving significant improvements in the production performance of closed gas reservoirs.
Future Challenges and Required Research
Closed gas reservoirs represent one of the greatest challenges in oil resource development. There is still a need for further research to understand the complex mechanisms associated with gas flow, especially under water leakage conditions. Such research helps improve production strategies and develop modern treatments to enhance production efficiency and ensure its long-term sustainability.
Future Challenges: How to manage water trapped in reservoirs and improve the effectiveness of hydraulic fracturing techniques. Additionally, it’s essential to develop more precise technologies for measuring TPG under various conditions, such as changes in pressure, managing gas flow intensity, and relying on mathematical models to describe the complex relationships between variables. Future research should focus on integrating new and improved technologies to identify the factors that affect gas production and effectively enhance the performance of closed gas reservoirs.
Effect of Water on Induced Pressure in Tight Gas Reservoirs
Induced pressure (TPG) is a fundamental factor in understanding gas flow dynamics in tight reservoirs with low permeability. Water significantly contributes to changing the gas flow properties within rocks, and this element is one of the important factors that many scientists overlook when creating mathematical models to estimate induced pressure. Multiple mathematical models have been developed to study TPG, but most focused either on rock properties or fluid properties in isolation, without considering the interaction between the two.
Studies have shown that induced pressure depends significantly on the level of water saturation in the rocks. When the water saturation level is high, the average pressure required for gas flow increases. For example, previous experiments conducted in the Ordos Basin showed that TPG is closely related to the amount of water present in the pores. Data derived from these experiments indicate that induced pressure rises significantly with increasing water saturation, attributed to the emergence of capillary effects, where small gas bubbles lead to an increase in hydraulic resistance.
It is also worth noting that the relationship between TPG and rock properties such as permeability cannot be ignored. As permeability decreases, TPG increases under the same water saturation conditions. This means that when the ability for gas to flow decreases, the need for higher pressures to push gas through the pores becomes greater. For example, in the case of rocks with permeabilities less than 0.1 milli-Darcy, those studies found that TPG was higher and significantly so compared to rocks with higher permeability, demonstrating the importance of the permeability factor in determining the effectiveness of gas extraction from tight reservoirs.
Dynamic Induced Pressure Measurement Testing Methods
In this research, a dynamic induced pressure testing device was used, specifically designed to operate under water-saturated conditions in tight gas reservoirs. This type of testing requires advanced measurement techniques that help achieve accurate results. A mixed method was employed, combining enhanced bubble methods with pressure difference measurement techniques.
The experiment began with preparing rock samples taken from various reservoirs in the Ordos Basin, where porosity and permeability were measured using different methods, including the Boyle method. After preparing the samples, the water saturation process was conducted by injecting water at a certain pressure to ensure that all pores were filled with water. A constant confined pressure was then applied in preparation for the dynamic tests, while adjusting the back pressure of the water used in the experiment. This setup ensures stable testing conditions and prevents any potential leakage of water or gas.
During each pressure stage, accurate measurements of gas flow rate and pressure were required, with flow curves obtained by gathering that data throughout the test. Efforts were also made to maintain a constant water saturation ratio during the operations, making the resulting data reliable and accurately reflecting the impact of water on induced pressure.
All procedures were documented in detail to ensure that experiments could be replicated by other research teams, enhancing the reliability of results and forming a basis for further studies in this area. In this way, a deeper understanding of the effects of varying pressures and water distribution in rocks on gas movement can be achieved, contributing to improved gas extraction strategies from tight reservoirs.
Results
Analysis of the Impact of Water Saturation on TPG
The aggregated results from the tests show a significant impact of water saturation on TPG in tight gas reservoirs. Any increase in the water saturation level in reservoir rocks directly affects the capillary pressure, such that rocks with low permeability exhibit higher capillary pressure frequencies compared to rocks with high permeability. This indicates that the design of exploration and extraction strategies should carefully consider the level of water saturation and the characteristics of the rocks.
When measuring TPG across several paper models, the results demonstrated that at a water saturation of 60% and 15 megapascals, nonlinear curves were documented, indicating the interaction of gas with water in the pores. The ability for gas to flow under these conditions depends on the pressure level and the amount of water that increases resistance. It was also shown that factors influencing TPG include permeability and saturation, with results proving a close relationship between them.
The data analysis process was executed precisely, utilizing statistical analysis techniques to identify regressions and general trends. Some layers were found to retain higher TPG levels as water saturation increased to maximum levels, due to excess pressure and the ability to adjust flow characteristics. A comprehensive analysis of the rock model with varying water saturation effects provides a framework for understanding how to better manage reservoirs to achieve higher gas extraction efficiency. This scientific aspect is significant for planning future production development plans.
NMR Spectrum Comparison of Three Layers
Nuclear Magnetic Resonance (NMR) spectrum is a powerful analytical tool used to study the physical and chemical properties of materials. When it comes to tight gas rocks, NMR is used to obtain accurate information about the internal structure and porosity distribution. Comparing the NMR spectrum of three layers of rock can reveal differences in physical properties such as porosity and permeability, which directly affect the productivity potential of resources. Through precise analysis of the NMR spectrum, the impact of pressure and water saturation on the capillary pressure gradient (TPG) can be evaluated, assisting in the optimization of gas field development strategies. In this analysis, the relationship between pressure, water saturation, and various rock properties is studied through the NMR spectrum.
Impact of Formation Pressure on TPG
The capillary pressure gradient (TPG) is influenced by formation pressure, a critical measure for understanding the gas flow in rocks. During experiments conducted on rock cores under varying pressure conditions, the gap between the surrounding pressure and pore pressure was kept constant. The results showed a decrease in TPG with increasing formation pressure, particularly in rocks with low permeability. In such environments, sliding phenomena increase, improving gas permeability in the rocks. At low formation pressure, TPG shows a significant decrease until the local pressure reaches 25.0 megapascals, at which point the sliding phenomenon significantly weakens. This change may be attributed to increased gas density affecting gas flow behavior, making it important to study the impact of formation pressure in developing tight gas fields and understanding how to handle different pressure variables.
Establishing a Mathematical Model for Dynamic TPG
Establishing a mathematical model for the capillary pressure gradient helps to represent the relationship between TPG, water saturation, and formation pressure. Experimental data are used to create an accurate model that can be relied upon to predict gas flow behavior in rocks. The equations used in the model depend on a suite of parameters obtained through the fitting process. Using this data, the quantitative relationship between TPG and various rock properties such as permeability is derived. This model represents a valuable tool for modeling gas flow under various pressure and saturation conditions, enabling researchers and engineers to enhance gas extraction strategies more efficiently.
Verification
From the Model
Verifying the accuracy of the derived model is a crucial step to ensure its credibility. By comparing the predicted results using the current model with the experimental results collected, the effectiveness of the model in describing gas flow behavior can be estimated. There was a good match between the theoretical values and the direct measurement results, reflecting the model’s ability to represent the actual conditions. This model is considered a powerful tool in various practical applications and can be used to guide drilling and extraction operations, as the pressure gradient is a critical factor in improving the productivity of gas fields.
Conclusion
The study demonstrated that the factors affecting the pressure gradient include water saturation and formation pressure, with water saturation having a greater impact on TPG. The results also indicate that an increase in formation pressure leads to a decrease in the rate of change in TPG until it stabilizes at a certain level. These results highlight the importance of considering water saturation rates when formulating strategies for developing tight gas fields. The study also encourages continued research into applying new methods to enhance TPG models, as actual production data must be used to improve models and confirm their accuracy under various geological conditions.
Hydraulic System Structure in Tight Reservoirs
Tight oil reservoirs are one of the essential components in the oil and gas industry, as they represent geological formations that contain limited amounts of hydrocarbons trapped in small spaces. Understanding the hydraulic structure of these reservoirs is vital for assessing production potential. Factors affecting fluid flow include permeability, rock properties, formation pressure, and water trapped within the pores. Both permeability and rock characteristics play a significant role in determining the effectiveness of the oil extraction process. For instance, the hydraulic gradient resulting from pore throats is significantly influential on flow rates, making it essential to study the properties of each reservoir individually.
Over numerous studies, the relationship between pressure and flow has been identified, representing a major challenge in tight gas production. In this context, pressure refers to the driving force behind fluid flow, while transport in rocks is expressed through coefficients such as permeability and oil viscosity characteristics. For example, some studies use mathematical models to analyze the behavior of gas and water flow within tight rocks, aiding in predicting well performance under certain conditions. When considering special cases such as dynamic effects, this is regarded as a key element in simulating fluid behavior.
Moreover, factors such as the mineral composition of rocks and geological changes determine the history of the geological reservoirs’ formation, affecting subsequent performance during drilling and production operations. Recent research demonstrates the importance of pressure’s effect on rock permeability, as varying pressures play a pivotal role in enhancing oil and gas flow. Understanding these complex, interrelated factors can lead to improved extraction strategies and increase profitability in drilling operations.
Challenges of Gas and Water Extraction in Tight Reservoirs
Extracting gas from tight reservoirs is considered one of the major challenges in the oil industry. The unique situation of tight reservoirs requires advanced techniques to understand and manage the dynamic behavior of trapped fluids. Engineers and geologists face several challenges regarding how to recover gas as efficiently as possible. Among these challenges is the hydraulic pressure barrier and the interference of water with gas, complicating the production process. This is due to the fact that the presence of water can affect the gas’s production capacity due to competition for space in the pore system.
Distributing
The fluids in tight reservoirs are uneven, complicating the flow process. In some cases, water is trapped under high pressure, meaning certain tactics must be applied to ensure the gas flow is not obstructed. Studies have shown that variable hydraulic gradients significantly impact the movement capacity within rocks, while pressurized water adversely affects production by creating attractive forces with gas. Scientists use models to calculate the pressure requirements needed to stimulate oils stored under various pressures, emphasizing the importance of accurately analyzing how these different fluids interact with each other.
Addressing the challenges of extracting gas from tight reservoirs involves the use of modern techniques, such as hydraulic fracturing and the use of chemical additives to enhance flow characteristics. These processes require significant investments and careful planning to mitigate risks and increase extraction success rates. Furthermore, these mechanisms require environmental considerations, as any process that may lead to pressure water leaks or contaminants in the surrounding environment could have widespread negative implications. Therefore, efforts are being made to develop new technologies that protect the environment while improving production performance.
Pressure System and Its Impact on Production
At the core of extraction processes, the pressure system is a pivotal factor that affects production. Pressure plays a key role in determining how fluids flow within tight reservoirs, with increased pressure serving as a catalyst for boosting production, but it depends on the balance between the gas stock and the pressure of surrounding rocks. Understanding how these factors interact can enhance economic returns and speed up the response of production operations.
Practical applications of production processes require understanding the relationship between applied pressure and permeability. When gas is exploited, a balance is achieved between natural and applied pressure, allowing both stability and dynamics during the extraction step. In this context, research has shown that increased pressure plays a crucial role in enhancing gas flow rates, as tight reservoirs are characterized by severe restrictions on the actual opening areas within the rocks. Thus, efficiently managing hydraulic pressure improves long-term performance. Additionally, smart use of modern technologies enhances effective pressure control during extraction processes, reducing the potential loss of gas during various stages.
Furthermore, the influence of external factors on pressure, such as temperature and humidity, must be considered, as changes in these factors can lead to adjustments in pressure within the reservoir. Maintaining stable pressure is vital to avoid complications that could lead to well closures or reduced production rates. Utilizing strategies that balance environmental performance and production is the path to achieving sustainable success in the gas industry. After reviewing this important aspect, we must continue exploring new technologies and innovative production methods to ensure resource sustainability and energy availability in the future.
Source link: https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2024.1487433/full
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